As bit rates increase in broadband data systems, the adverse effects of a communication conduit (e.g., a copper cable) are increased. For example, skin effect and dielectric loss in copper cables results in jitter and attenuation of transmitted data at high frequencies. Such loss results in errors in receiving and decoding signals. These losses increase as cable lengths increase.
Equalizers can be used to compensate for communication conduit degradation. An equalizer may be used to boost a signal within a desired frequency range. For example, an equalizer may boost the energy of a high frequency range of a signal to compensate for high frequency attenuation due to a communication conduit. Typically, equalizers include a control signal that may be used to adjust the amount of compensation provided by the equalizer. The control signal may be provided by an adaptive controller, which adjusts the control signals based on an analysis of the signal output by the equalizer. Such an adaptive equalizer is particularly useful when the characteristics of the communication conduit are not predetermined.
An example prior art equalizer 100 is illustrated in FIGS. 1A and 1B. The example equalizer 100 includes a fast path stage 102, a slow path stage 104, and a mixer stage 106. The fast path stage 102 includes a peaked amplifier, which is used to provide a predefined gain to a high frequency portion of an input signal Vin. The slow path stage 104 includes a flat response amplifier, which provides a predefined gain to a low frequency portion of the input signal Vin. The output signals of the fast path stage 102 and the slow path stage 104 (i.e., Vfast and Vslow, respectively) are coupled to the mixer stage 106, which mixes Vfast and Vslow based on a variable weighting of the signals set by a control signal Vcontrol.